Voltage regulating device



L. BODDY 2,

VOLTAGE REGULATING DEVICE? May 6, 1958 2 Sheets-Sheet 1 Filed Aug. 55, 1955 l I; I

IN V EN TOR.

l4 BY I arm /s" y 1958 L. BODDY 2,833,889

VOLTAGE REGULATING DEVICE Filed Aug. 3, 1955 2 Sheets-Sheet 2 mz j lNVE NTOR E- MMWJ United States Patent Ofiice 2,833,889 Patented Ma a, .1958

, VOLTAGE REGULATING DEVICE Leonard Boddy, Ann Arbor, Mich., assignor to King- Seeley Corporation, Ann Arbor, Mich., a corporation of Michigan Application August 3, 1955, Serial No. 526,190

8 Claims. (Cl. 200--122) as the primary support means for a pair of electrical contact elements, as the primary support'means for means for controlling the position of each of those contacts, and as the primary support means for means for adjusting the contact forces.

A further feature of this invention is an improved means for mounting each of a pair of cooperating electrical terminals.

The manner of accomplishment of the foregoing object, the nature of the above features, and other objects and features ofthe invention, will be perceived from the following detailed description of embodiments of the invention when read with reference to the accompanying drawings in which:

Figure l is a view in top plan of a preferred construction of thermally responsive regulator embodying the principles of the invention;

Fig. 2 is a view in vertical section of the structure of Fig. 1, taken along the line 2-2 of Fig. 3;

Fig. 3 is a view in horizontal section, taken along the line 3-3 of Fig. 2;

Fig. 4 is a fragmentary view in vertical section, taken along the line 4-4 of Fig. 1;

Fig. 5 is a view in horizontal section of another embodiment of the invention;

Fig. 6 is a sectional view taken substantially along the line 66 of Fig. 5;

Fig. 7 is a sectional view taken substantially along the line 77 of Fig. 5;

Fig. 8 is a sectional view taken substantially along the lineS-S of Fig. 5; and

Fig. 9 is a'view of one'of the elements represented in Figs. 5 to 8 priorto'installation.

This application is acontinuation-in-part of a part of my application SerialNo. 108,773, filed August 5, 1949, relating'to Electrical Control Apparatus, and of the continuation thereof, Serial No. 658,888, filed May 13, 1957. Details of the circuit characteristics of the herein disclosed regulator and of exemplary electrical circuits of which the present device may be a part are described in detailin the aforesaid application and a circuit including the herein disclosed regulator, -a-vo'ltage'source, and a load is disclosed in my Patent 2,762,997, granted'September 11, 1956. p

It will be appreciate'dfrom a completeunderstanding of the present invention that the'improvements' -thereof types of energy supply sources.

can, in a generic sense, be embodied in electrical control systems of widely differing types, for association with widely differing types of load circuits and widely differing The illustrated embodiment of the present invention has been specifically designed to be an element of a system for gauging engine temperature, oil pressure and gasoline supply conditions in automotive vehicles. Such use is, of course, to be regarded in an illustrative and not in a limiting sense.

Basically, the disclosed regulator can be characterized as including a thermally responsive member atleast :a portion of which tends to move as a consequence of chan es in the temperature thereof. Current modulating means are associated with this member so as to respond to the tendency to move. The current modulatingmeans serve to increase the heating current supplied to the regulator .in response to decreases in temperature thereof and vice versa. Consequently, throughout at leasta predetermined range of voltages of the source, the-current modulating means periodically increase and decrease the current supplied to the thermally responsive member and cause it to be maintained ata substantially uniform averagetemperature. On this basis, it will be appreciated that the thermally responsive member receives energy, in pulsating form, at a substantially uniform average rate. This energy rate may, of course, be expressed as E /r, E being the effective or root-meansquare voltage of the energy pulsations and r being the electrical resistance of the regulator. Under any given ambient temperature condition, the electrical resistance of the regulator may, for all practical purposes, be regardedas constant. Consequently, for any given ambient temperature condition, the effective voltage of the energy pulsations absorbed by the regulator is also substantially constant and independent of variations in the voltage of the associated source of energy. The control ofthe effects of ambient temperature changes, as well as the advantage which may be taken thereof are set forth in the aboveidentified copending application.

The herein disclosed improved regulators can further be characterized in that they are adapted to have :the associated gauging or load circuits connected theretotin parallel with the current consuming elements of .the regulator, and subject to the current modulating means. Consequently, the load circuits also receive energy pulsations having an effective voltage which is substantially independent of variations in the source voltage. The .arrangernent is such that load currents have no appreciable heating effect upon the thermally responsive element. Consequently, the effective voltage established by the regulator is independent of the relative magnitudes of the heating and load currents, and the load currents may be individually varied at random without affecting in any way the action of the regulator.

In general, the regulatorcomprises a thermally responsive tri-metallic element 40, which carries a heater winding 42. One terminal of Winding 42 is grounded, and the other terminal thereof is electrically connected to the element 40. In this instance the current modulating means comprises a pair of contacts 44 and 46 and a shunt resistor 70. The element 40 carries the movable contact, which normally engages the fixed contact 46.

By applying a suitable voltage between contact 46 and grounded casing of the regulator, current is made to flow through contacts 46-44, the body of the element 40 and the heater winding 42 to ground. Completion ofthis circuit supplies heat to the element 40 and causes its temperature to rise. As is discussed in more detail be low, the electrical resistance of the element 40 is so low that for all practical purposes, allof the heating elfect can be considered as being derived from the winding 42. With this relation, element 40 can also serve as a conductor of the gauging and heating currents.

Upon being heated, the element 40 warps and separatesthe contacts 44 and 46, interrupting the just traced circuit and also reducing the heating effect. The reduction in heating efiect enables the element 40 to cool and restore the contacts 34-46 to closed condition. So long, acordingly, as voltage is applied, contacts 44-46 are periodically opened and closed and the heating current is correspondingly modulated. Consequently, the element 40 acquires a temperature just high enough to hold the contacts 1-4-46 in a condition of incipient closing and opening. This critical temperature can be variously determined, as an incident to manufacture,

by adjusting the position of the fixed contact 46 relative tothe contact 44, so as to correspondingly determine the initial pressure between these terminals. For automotive work, it is usually preferred to adjust the regulator 16 to provide a regulated or effective voltage of about 5v0lts. Consequently, neglecting ambient effects, the regulator acts to receive from the source an amount of electric energy, in pulsating form, which has a substantially uniform heating value. On this basis, and since, over any period of time, the wattage input to the regulator heater (E /r) is at a constant rate, it is evident that the regulator breaks up the energy supplied by the source into a succession of pulses having an eifective voltage which is independent of variations in the voltage of the source.

The voltage impressed across winding 42, between terminal 44 and ground is, of course, equal to the voltage impressed upon any gauging circuits connected in parallel therewith. These circuits, therefore, are supplied from the source with pulsating energy at an effective voltage which is substantially independent of variations in the voltage of the source. The regulator thus effectively serves as a regulator of the voltage impressed across the gauging circuits, and currents drawn by the individual gauging circuits are thus independent of variations in voltage of the source.

In the interest of economy of manufacture, the element 40 desirably serves as a conductor of both the heating and load currents, so that the winding 42 as well as the load circuit can be directly connected to the element 40, as 'by a spot welding operation or otherwise. In this event, it is important, as aforesaid, that the electrical resistance of the element 40 be so low that for all practical purposes all heating effect thereon can be regarded as derived from the winding 42. In the preferred practice of the invention, the element 40 is of trimetallic form. It may, for example, embody outer elements composed, respectively, of a material having a high coeflicient of expansion, such as a comparatively high chromium alloy, and a material having a very low coeflicient of expansion, such as Invar. The intermediate layer may be material such as copper or nickel having very low electrical resistance. Relative thicknesses of the various materials may, of course, vary. For example, a trimetallic strip having a thickness of .0095 inch may be formed of an Invar strip having a thickness of approximately .0025 inch, an intermediate layer approximately .0025 inch thick and a high coefficient outer layer approximately .0045 inch thick. The intermediate layer, being on the neutral axis of the composite strip, does not materially interfere with deflection thereof, but it does afford a good low resistance conductor through the strip. Additionally, the intermediate high conductivity layer improves the heat conductivity characteristics of the strip and increases the speed of response thereof.

In a preferred form, the elements of the regulator are mounted within a sealed enclosure constituted by upper and lower cup-shaped members 80 and 82 which may, for example, be formed of light weight metal stampmgs. Preferably, and as illustrated, a sealing gasket 81 is interposed between these casing members. Element 40 is illustrated as being of U-shaped form, having one leg 34 which carries the previously identified Winding 42, and a companion compensating leg 86. Leg 86 is anchored at its free end to a headed rivet 88 which serves to electrically connect leg 86 to the exposed terminal 90. It will be appreciated that changes in ambient temperature conditions have like effects upon the two legs 8486 and cause the connecting bridge 85 to rise and fall, without (except as noted below) altering the position of the contact 44. Current flowing in winding 42, on the other hand, causes leg 84 to warp relative to leg 86 and move contact 44.

For mounting stability terminal 90 has a laterally extending, downwardly deflected leg 94 which is held in place by the companion rivet 96.

As aforesaid, the free end of leg 84 carries the previously identified movable contact 44. The companion fixed contact 46 is carried near one end of the free leg 98 of a U-shaped spring strip 100. Leg 98 extends parallel to and is immediately above the leg 34, as viewed in Figs. 2 and 3. The other leg 102 of spring strip is anchored to the casing by the previously identified rivet 96, and is electrically connected thereby to the companion terminal 104. Terminal 104 is provided with an upstanding lug 106 for connection to an input lead. As in the case of terminal 90, terminal 104 is provided with a laterally extending downwardly deflected leg 108 which is anchored in place by the previously identified rivet 88.

The mounting spring strip 100 for the fixed contact 46 is preformed so that it tends to bow downwardly as viewed in Fig. 2 and press against the movable contact 44, thereby preloading the element 40. The free end of leg 98 of spring strip 100 cooperates with an adjustable stop 110 which limits the downward movement thereof and which, it Will be appreciated, can be adjusted as an incident to final inspection to determine the amount of preloading of the bimetallic element. This adjustment determines the temperature which the regulator must attain in order to effect a separation of the contacts, and, consequently, determines the regulated voltage of the system. Adjusting screw 110 is carried by an L-shaped mounting member 112 which is carried by the rivet 88, but is insulated therefrom, as well as from the bimetallic element 40, by insulators 114 and 116.

Rivet 88 also carries, in electrical contact with the element 40, a resistor mounting clip 118. A companion clip is carried by rivet 96, in'electrical contact with the mounting spring strip 100, which carries the fixed contact 46. Mounting clips 118 and 120 are thus electrically connected, respectively, to the contacts 44 and 46, and may serve as a mounting for a resistor or as a convenient means of connecting a condenser or other means across contacts 44-46, for the purpose of sup pressing any tendency to cause radio interference.

As previously noted, one end of heater winding 42 is spot Welded or otherwise electrically connected at 122 to the bimetallic leg 84, and the other end is correspondingly grounded to the casing 80 at 126. The casing as a whole may be mounted, and grounded, by bracket 83.

Coming now to a consideration of the effect upon the elements of the present system, of substantial changes in ambient temperature, it will be appreciated that, as aforesaid, the regulator 16 acts to maintain a leg 84 thereof at a substantially uniform average temperature, just high enough above ambient temperature to maintain contacts 4446 in a condition of incipient opening and closing. The rate of exchange of heat between any two bodies (for example, tri-metallic element 40 and its enclosing casing) is, of course, proportional to the difference between the fourth powers of the respective absolute temperatures of the bodies. On this basis, the rate of heat loss from leg 84 increases with increases in ambient temperature, and vice versa. Consequently, in order to maintain the aforesaid average temperature of leg 84, the rate aeaeg sss vice versa.

Assuming that the resistance of winding 42 is independent of ambient changes, it will be appreciated that this increase in wattage is accomplished by an increase in the effective voltage of the energy pulsations received by winding 42. More particularly, the ratio of the effective voltages at two different ambient temperatures is equal to the square root of the ratio between the wattage requirements of the regulator at the same two ambient temperatures.

Therising or falling efifective voltage characteristic of the regulator, resulting from the increase or decrease in wattage requirements of the regulaton which acompany increases or decreases in ambient temperature can, of course, be increased by utilizing a heater winding 42 which has a positive temperature coefiicient of resistance. This is because increases in resistance of the winding 42, for any given wattage requirement, must be accompanied by an increase in the effectivevoltage of the regulator, and vice versa.

Also, the aforesaid rising or falling voltage characteristic of the regulator may be increased or decreased by adjusting the length of the compensating leg 86 relative to the length ,ofthe operating leg 84 was to, in effect, over or undercompensate the regulator. More particularly, in the disclosed arrangement, ifcompensating leg 86 is shorter thanle g 84, the regulator would, in the absence of the varying rate of heat loss occasioned by ambient changes, have a voltage characteristic which, falls in response to increases in ambient temperature, and vice versa. Convers ly, ifleg 86 is longer than leg 84, the regulator would, even in the absence. of the'changed rate of'heat loss, have arising voltage characteristi'c'in response to increases in ambient temperature, and vice versa. It will be appreciated that theserelationships may be modified, even to the extent of reversal, if different structural arrangements are employed. Thus, the direction and the magnitude of the changes of the voltage characteristics of the regulator may be varied not only by appropriate selection of the relative total lengths of the two bimetallicor polymetallic legs 84 and 86 (Fig. 3), but may also be varied by changing the temperature-responsive defiectional characteristics of a portion of .either leg.

As an example, a portionof either leg maybe monometallic, or maybe polymetallic but prevented from flexing by suitable means such as a longitudinal deformation or an upstanding fiange similar to the flange on bridge .85.

Further, even if both legs be polymetallic, substantially equal in length and parallel, substantially as shown in Fig. 3, the direction and magnitude of the temperature-responsive changes in the voltage characteristics of the regulator may be selected by varying the angles between the legs ,84 and 86 of the bridge or crosspiecefi85, the magnitude of the change varying as the included angle between, for example, leg 84 and bridge 85 varies from theshown 90 angle, and the direction of the change being determined by whether that included angle is acute or obtuse.

Other means for varying the magnitude and direction of the changes in the voltage characteristics ofthe regulator with changes of ambient temperature will be apparent to those skilled in the art as a result of the teachings of the foregoing examples.

It will be appreciated, therefore, that the normal rate vof change in the effective voltage of the regulator, occasioned only by the varying rate of heat loss, can be either increased, reduced or, in fact, reversed, depending upon the temperature coefiicient of resistance of the winding 42 and the relative proportioning of the'tri-metallic legs 84 and86.

Themodified form of the invention represented inFigs. 51to 9 of the drawings differs from the first-described embodiment primarily in that the clips 118 and 120 have been omitted, and in the manner of adjusting the position of the fixed contact 46. Those parts or portions which ment of the cam 144.

:are identical'or similar in both torms have identical reference characters applied thereto.

While the provision of clips 118 and 120 (Figs. 2 to 4') may in some circumstances be desirable to permit the ready mounting of a resistor or capacitor inshunt ofthe electrical contacts, these elements are not essential to the proper functioning of the device and may be either included in or omitted from either of the disclosed, or equivalent, forms.

In the modified embodiment represented in'Figs. '5 -to-9 of the drawings, the fixed contact 46 is supported on a generally U-shaped spring strip 100, with oneend of leg 102 of that strip 100 being fixed relative to the upper cupshaped member by rivet'96. Leg 136 of strip is provided at its unsupported end with a hat, generally triangular, contact-supporting surface 138 (Fig. 5)'one edge of which bears an upstanding flange 140 (Figs. '6 and 7) the height of which varies along its length. Flange 140 in turn supports a ramp 142 the upper surface of which is roughly rectangular. All of the constituent parts of element 100, including portions 102, 136, 138, 140 and 142, may be and preferably are stamped and formed from a single sheet of stock. Phosphor bronze is an example of a suitable material.

Ramp 142 is engaged by a cam 144 (Figs. 6 to 8) mounted on an adjusting arm 146. Adjusting arm'146 is integral with but disposed at an angle toan upstanding leg 148 which is provided with a laterally'projecting apertured base portion 150. Base portion maybe associated with rivet 88 in the same manner as member 112 (Fig. 4) is associated with its rivet 88 in the firstdescribed embodiment ofthe invention, i. e., mechanically fixed but electrically insulated. Alternatively, 'an'eyelet may be fastened within the aperture in thebase portion 150, with that eyelet being mechanically held' by but 'insulated from the rivet 88. Again, the elements 144, 146, 148 and 150 may be and preferably are stamped and formed from a single strip of stock, such as cold rolled steel.

The adjusting arm 146, the leg 148, or both, is bendable to swing the cam 144 through an are about an axis parallel with the longitudinal axes of the rivet 88 and of the leg 148. This axis may be along the longitudinal center .line of the leg 148, about the line of junction betweentheadjusting arm 146 and the leg 148, or elsewhere. Obviously, the process of bending may cause a shift in the position of this axis in some cases. Exemplarily, the leg 148 is slotted, as at 154 (Figs. 6 and 7) to reduce its torsional strength. It will be noted that while base 150 is preferably nonrotatively associated with rivet 88, the requisite adjust ment can also be obtained by rotating base 150 relative to rivet 88, without bending portions 146 and 148, although the preferred arrangement tends to provide a more stable adjustment.

The shape of surface 138 (Fig. 5) of element 100 is selected to so position ramp 142 that it will be engaged by cam 144 over a considerable amplitude of the substantially arcuate adjusting movement of that cam. The shape of flange 140 is selected to provide the requisite inclination of the ramp 142 so as to achieve the desired amplitude of movement of the fixed contact 46 with the desired or available amplitude of the substantially arcuate moveit will be noted that thegreater the ratio of cam-to-fixed-contact movement the -more easily-precise adjustment can be obtained.

Adjusting arm 146 and cam 144 may be considered to remain always at a fixed distance from, for example, the face of the upper cup-shaped member 80. Ramp 142 is continuously maintained in engagement with cam 144 by appropriately preforming the strip100. In the disclosed arrangement, sharp bends are established at two places in leg 136 during the manufacture of the strip 100. The configuration of element 100 prior to installation is represented in Fig. 9 of the drawings. Approximately along the line of junction between leg 136 and the curved portion of strip 100, the leg 136 is bent away from the plane of leg 102, and at a point towards the free end of leg 136 but short of the surface 138, leg 136 is bent in the other direction. In the representative showing, the latter angle is less than the former, and is such as to establish substantial coplanarity between the surface of the ramp 14-2 and the surface of the major portion of the leg 136, although it will be recognized that these angles will vary with variations in the thickness and characteristics of the spring-metal employed, and with variations in the desired position and desired pretensioning of the parts when assembled.

By virtue of the described bending, strip 100, when installed, will continuously exert forces to hold ramp 142 in engagement with cam 144. These forces are large relative to the opposing force applied by the pretensioned spring 40 through contacts 44 and 46 to the surface 138, so contact 146 is effectively fixed against movement relative to the body of the regulator except for intentional adjusting.

It will be observed the adjustable limit-stop function served by the disclosed cam arrangement can be performed by any other arrangement in which the plane of movement of one part is inclined to the plane of the surface engaged by that part. As one example, surface 142 can be parallel with the support surface portion of the upper cup-shaped member 80 and leg 148 may be disposed at an acute angle to its base 150 and hence to the support surface.

While it will be apparent that the embodiments of the invention herein disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. In a thermally actuated device, a support surface, a first and a second terminal, means fixing said first terminai to said support surface, fastening means fixing said second terminal to said support surface in spaced proximity to said first terminal, an arm on said first terminal connected to said fastening means, a first spring member, means including said first terminal fixing means for fixing one end of said first spring member relative to said support surface, a first electrical contact on the other end of said first spring member, a second spring member, means including said fastening means for fixing one end of said second spring member relative to said support surface, a second electrical contact on the other end of said second spring member engageable with said first electrical contact, means including said first spring member for applying a force tending to move said first electrical contact into engagement with said second electrical contact, means including said second spring member for applying a force tending to move said second electrical contact into engage ment with said first electrical contact, said first spring bein deformable in response to applied heat, means for applying heat to said first spring, and adjustable means for limiting the movement of said second electrical contact towards said first electrical contact.

2. In an electrothermal device for supplying a controlled voltage to a load having two terminals from a source of variable voltage having two terminals one of which is connected to one terminal of the load, the cornbination of a casing, a unitary U-shaped polymetallic element having first and second substantially parallel leg portions and a relatively rigid crosspiece interjoining one end of said first leg portion and one end of said second leg portion, first fastening means including a member electrically connected to the other end of said first leg portion for mechanically fixing said other end of said first leg portion to said casing, a first electrical contact mounted on the other end of said second leg portion, a second electrical contact, support means forsupporting said second electrical contact in spaced relation with said casing and in mateable relation with said first electrical contact, second fastening means for securing said support means to said casing, said second fastening means being electrically connected with said second electrical contact, an electrical resistance type heater wire disposed in heat transfer relation with one of said leg portions, means for electrically connecting one end of said wire to said first fastening means, a metallic element, means for electrically connecting the other end of said wire to said metallic element, and insulating means for electrically insulating both of said fastening means from one another and from said metallic element, said polymetallic element holding said first electrical contact in engagement with said second electrical contact when said leg portions are at substantially the same temperature and moving said first electrical contact from engagement with said second electrical contact in response to differential heating of said leg portions by said heater wire, said first fastening means being connectable to the other terminal of the load, said metallic clement being connectable to the terminal of the voltage source which is connected to the one terminal of the load, said second fastening means being connectable to the other terminal of the voltage source.

3. The combination of claim 2 in which said metallic element is an integral part of said casing.

4. The combination of claim 2 in which said casing is provided with a cover so that said polymetallic element is enclosed and in which both of said fastening means extend through said casing so that electrical connections can be made thereto exteriorly of said casing.

5. The combination of claim 2 in which said means for electrically connecting one end of said wire to said first fastening means includes a major portion of the total length of said polymetallic element.

6. The combination of claim 2 in which said second electrical contact is movable relative to said casing to adjust the relationship between said electrical contacts and to vary the average magnitude of the controlled voltage.

7. The combination of claim 6 in which said support means is an elongated. member having one portion engaging said second fastening means and a second portion to which said second contact is secured and a third portion engageable and movable by an adjusting means.

8. The combination of claim 7 in which said adjusting means is manually rotatable about an axis spaced from said electrical contacts to shift the position of said second electrical contact.

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